add modules 5-9

08-testing/tests/static/README.md

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+# Static checks
+
+## Built in
+
+### Format
+Enforces style rules for your configurations.
+```
+terraform fmt -check # checks if formatter would make chances
+
+terraform fmt # applies those changes
+```
+
+### Validate
+Checks that configuration are valid.
+
+Terraform init is required to use validate. If not working with a remote backend, `terraform init -backend=false` can be used.
+```
+terraform validate
+```
+
+### Plan
+Looking at the resulting Terraform plan can help catch bugs.
+```
+terraform plan
+```
+
+### Custom Validation Rules
+Enforce conditions on variables to prevent misuse
+```
+variable "short_variable" {
+  type = string
+
+  validation {
+    condition = length(var.short_variable) < 4
+    error_message = "The short_variable value must be less than 4 characters!"
+  }
+}
+```
+
+## External
+
+There are many 3rd party tools which can check Terraform configurations for potential issues and/or suggest best practices:
+- [tflint](https://github.com/terraform-linters/tflint)
+- [checkov](https://github.com/bridgecrewio/checkov)
+- [terrascan](https://github.com/accurics/terrascan)
+- [terraform-compliance](https://terraform-compliance.com/)
+- [snyk](https://support.snyk.io/hc/en-us/articles/360010916577-Scan-and-fix-security-issues-in-your-Terraform-files)
+- [Terraform Sentinel](https://www.terraform.io/docs/cloud/sentinel/index.html)